Robotic apparatus

ABSTRACT

A robot for performing a working operation on a surface. The robot comprises a frame which supports a pair of parallel tracks. An endless link chain is mounted for travel on each track and each chain is driven by an independent motor mounted on the frame. Each track is provided with at least two recesses with each recess having an open side facing the respective chain. A series of vacuum cups are mounted on each chain and are adapted to engage the surface to be traversed. A first series of ports connect a first recess of each track and a first group of vacuum cups on each chain, while a second series of ports communicate between the second recess of each track and a second group of vacuum cups. A source of vacuum is connected to the recesses and acts through the ports to the respective vacuum cups to enable the vacuum cups to grip the surface. In a preferred manner of use, the robot is employed with a laser tracking system in the non-destructive inspection of an aircraft.

BACKGROUND OF THE INVENTION

Robotic devices have been proposed for performing a working operation,such as cleaning or polishing surfaces, that are not accessible tonormal manual operations. In general, the robotic devices have been usedon flat or planer surfaces such as windows, building panels and thelike. The typical robotic device includes a pair of endless belts ortracks, each carrying a series of vacuum cups. The belts areindependently and remotely driven to move the device across the surfaceto be treated, and a source of vacuum, such as a vacuum pump, isconnected to the vacuum cups to create a negative pressure within thecups so that the cups can grip the surface and enable the robotic deviceto move over inclined or vertical surfaces. A typical robotic device canoperate on smooth continuous surfaces but if the device moves across anobstruction or crack in a vertical or inclined surface, the vacuum maybe lost, resulting in the device falling from the surface.

Large commercial aircraft are normally washed and waxed every thirtydays. Because of the large size and shape of the aircraft it iscustomary to erect a scaffold along side the aircraft and a number ofworkers supported on the scaffold then hand scrub the outer surface ofthe aircraft. After scrubbing, the aircraft is waxed and polished usingmanual rotary buffers. The buffers are relatively heavy and due to thelarge surface area of the aircraft a buffing operation is a tedious andtime consuming operation. The entire operation of scrubbing, waxing andbuffing the aircraft usually takes a period of 20 to 30 hours utilizing10 workers.

Commercial aircraft are also subjected to a non-destructive inspectionafter 7,000 cycles of pressurization. Each take-off and landing in whichthe aircraft is pressurized is considered to be a pressurization cycle.In the typical non-destructive inspection, the paint is strippedentirely from the aircraft and the seams and rivets are manuallyinspected. If a defect is observed during the inspection, the area ofthe defect is marked and is subjected to an eddy-current sensor todetermine the magnitude of the defect. After the manual inspection theaircraft is repainted and subsequently waxed and buffed.

The normal paint stripping, inspecting, repainting and waxing operationis extremely time-consuming and labor intensive, resulting in asubstantial expenditure. As a further problem the paint strippingoperation presents a serious environmental problem, in that methylenechloride is generally used as the solvent to remove the paint and for alarge aircraft, such as a Boeing 747, upwards of 1,000 gallons ofmethylene chloride may be required to strip the paint from the aircraft.As methylene chloride is toxic and presents an environmental problem,pollution abatement equipment is necessary in order to remove thesolvent fumes from the paint stripping area.

SUMMARY OF THE INVENTION

The invention is directed to a robotic device for performing a workingoperation on a surface and has particular application to performing aworking operation on a contoured surface having surface irregularitiessuch as encountered in a commercial aircraft.

The robotic device Comprises a supporting structure or frame whichsupports an outer open bottom housing or hood. A pair of flexible tracksare mounted on the frame and an endless member, such as a link chain, ismounted for travel on each of the tracks. Each chain in independentlydriven by a separate motor which is mounted on the frame.

Each of the tracks is formed with at least two channels with eachchannel having an open side facing the respective chain. A series ofvacuum cups are mounted on each chain and a series of first ports areconnected between a first of the channels of each track and a firstgroup of vacuum cups, while a second series of ports providecommunication between a second channel of each track and a second groupof vacuum cups. The first and second groups of vacuum cups arepreferably in alternating sequence.

Negative pressure or a vacuum is applied to each channel and hencethrough the ports to the vacuum cups, thus enabling the cups to grip asurface to be traversed.

In a preferred form of the invention, each track is formed with two pairof side-by-side channels and the vacuum is applied independently to allfour channels. In this embodiment, a first series of ports in the chainregister with the first and third channels, while a second series ofports in the chain register with the second and fourth channels. As thevacuum is applied independently to the several channels, the roboticdevice can move over gaps or obstructions in the surface without losingvacuum in all of the vacuum cups. If for example, the device moves overa crack causing a loss of vacuum in one of the track channels, thevacuum will be retained in the remaining channels to thereby maintainthe device in gripping contact with the surface.

In a preferred embodiment the robotic device is employed fornon-destructive inspection of aircraft using a laser tracking system. Inthis embodiment one or more laser units are mounted on the groundadjacent the aircraft and a retro-reflector or cats-eye is mounted on asupport carried by the robotic device. The support is slidable relativeto the robotic device and is biased downwardly so that a shoe or sensorcarried by the support will ride against the surface of the aircraft. Asthe robotic device moves in the desired path of travel over the aircraftsurface, the sensor or shoe rides on the surface, and through the lasertracking system, the surface of the aircraft is mapped. The aircraft isthen pressurized and the surface is again mapped and any surfacedeviations, outside of a given tolerance, indicate possible defects inthe aircraft surface.

The use of the robotic device along with the laser tracking system, toprovide non-destructive inspection of a aircraft, eliminates the manualpaint stripping, visual inspection, repainting and waxing of theaircraft as is normally used and therefore substantially reduces theoverall time and cost of the non-destructive inspection. As a furtheradvantage, the method of the invention eliminates the use of toxicsolvents which are normally used to strip the paint from the aircraftand correspondingly eliminates the pollution control devices that arenecessary with the use of such solvents.

In a second embodiment of the invention the robotic device can beemployed to move a working implement over the aircraft or other surface.The working implement can be a rotary scrubber, buffer, paint sprayer,or the like. By utilizing the robotic device to perform these workingoperations the extensive hand labor normally required to wash, wax andor paint an aircraft or other surface is substantially reduced. As afurther advantage, a robotic device enables a constant application ofpressure to be applied through the implement to the surface thusproviding a more uniform cleaning and polishing operation.

The invention also can include a safety feature to prevent the roboticdevice from falling from the surface in the event of failure of thevacuum system. In this regard, a fan is mounted in an opening oraperture in the outer housing and if the magnitude of the vacuum dropsbeneath a preselected value, the fan is operated to create a negativepressure within the outer housing or hood to prevent the robotic devicefrom falling from the surface.

The robotic device of the invention has the advantage that it is capableof moving over surface deviations, such as obstructions or gaps withoutlosing vacuum. Moreover the frame is composed of flexible plasticmaterial which enables the robotic device to follow the curved contourof an aircraft or other surface to be treated.

Other objects and advantages will appear during the course of thefollowing description.

DESCRIPTION OF THE DRAWINGS

The drawings illustrate the best mode presently contemplated forcarrying out the invention.

In the drawings

FIG. 1 is a longitudinal section of the robotic device of the invention;

FIG. 2 is a section taken along line 2--2 of FIG. 1;

FIG. 3 is a section taken along line 3--3 of FIG. 2 and showing theconnection of the drive to one of the chains;

FIG. 4 is an enlarged fragmentary longitudinal section taken along line4--4 of FIG. 3 and showing the vacuum connection the vacuum cups;

FIG. 5 is a bottom view of the track with parts broken away;

FIG. 6 is an enlarged fragmentary longitudinal section showing theengagement of the chain with a drive sprocket; and

FIG. 7 is a schematic view showing the use of the robotic device alongwith a laser tracking system in the non-destructive inspection of anaircraft.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

FIGS. 1-6 show a robotic device 1 that can be employed to provide aworking operation on a surface 2. Surface 2 can either be a planer ornon-planer surface, such as an aircraft, building, bridge, storage tank,train or the like.

Robotic device 1 includes an outer open bottom housing or hood 3, whichis supported by an internal frame 4. Housing 3 is composed of arectangular side wall 5 and a generally flat upper surface or top 6,having an opening therein which is bordered by a generally curvedupwardly extending flange 7. A series of braces 8 extend diametricallyacross the opening in flange 7 and support a retro-reflector or cats-eye9 to be used in a laser tracking system, as will be hereinafterdescribed.

Secured to the lower edge of sidewall 5 is a strip 10 having adownwardly facing groove which receives the upper edge of a brush seal11, as shown in FIG. 3. Brush seal 11 includes a plurality of fine,synthetic, flexible bristles formed of a material such as nylon whichengage the surface 2 and provide a seal to the surface.

Frame 4 consists of a pair of inverted V-shape frame members 12 whichextend transversely of the housing 3 and each frame member 12 includesan upper flat section 13, which is secured to the under surface 6 ofhousing 3. In addition, each frame member 12 is provided with a pair oflower, horizontal flanges 14 and each flange 14 is secured to the upperflange 15 of a bracket 16, as best shown in FIG. 3. With thisconstruction there are four brackets 16 with a pair of the bracketsbeing located along each side of the device.

Each bracket 16 also includes a lower flange 17 which extends outwardlyand is secured to the upper surface of a flexible-track or guide 18, asseen in FIG. 3. Each track 18 is preferably formed of plastic materialand is connected between a pair of the brackets 16. In addition, a pairof braces 19 extend transversely of the device and connect the tracks 18together.

Tracks 18 serve to guide the lower run of an endless link chain 20 asshown in FIG. 3.

To drive the chains 20 in their endless paths of travel, a sprocket 21is mounted for rotation outwardly of each bracket 16 and the sprocketson each side of the frame are engaged with the respective chain. Eachsprocket 21 is carried by a shaft 22 which extends outwardly from therespective bracket 16, as shown in FIG. 3. The ends of each track, asillustrated in FIG. 5, are provided with longitudinal, open-ended slots23 which receive the respective sprockets 21.

One sprocket of each longitudinal pair is an idler sprocket, while theother sprocket 21 of each longitudinal pair is a driven sprocket. Todrive the sprockets 2lb, an electric motor 24 is located inwardly of thebracket 16 and operates through a gear box 25 with the output shaft ofthe gear box connected to the shaft 22 of the driven sprocket 21. Aseparate motor 24 is utilized with each driven sprocket 21. Thusoperation of the motors 24 acting through the sprockets 21 will drivethe respective chain 20 to move the robotic device in the desired pathof travel along the surface 2.

As best seen in FIG. 1 the upper run of each chain 20 is supported on aguide bar 26. A pair of rods 27 extend downwardly from each guide bar 26and the lower end of one of the rods is connected to the respectivetrack 18, while the lower end of the second rod is connected to amanifold block 28, which is mounted on the track 18. Coil springs 29 arelocated about the rods 27 and urge the guide bar 26 upwardly therebyacting to tension the chain 20.

The construction of each link chain 20 is best illustrated in FIGS. 3, 5and 6. Each chain 20 is composed of a series of pivotally interconnectedlinks 30 and a boss or tubular projection 32 extends outwardly from oneside of each link 30 and is received within a flanged recess 33 in theadjacent link. Pins 34 provide a pivotal connection between the boss 32of one link and the hinged recess 33 of the adjacent link. The hingedbosses 32 are adapted to be engaged by notches 35 in the respectivesprockets 21, as best seen in FIG. 6.

As shown in FIG. 3, the hinged connections 32 of chain 20 are guided formovement within a central groove 38 in track 18 and each chain link isprovided with a pair of outwardly extending ears or flanges 30a whichare received within guideways 38a in the track. The engagement offlanges 30a with guideways 38a prevents downward displacement of thechain 20 from track 18.

A series or row of vacuum cups 39 are mounted on the outer surface ofeach chain 20, as shown in FIG. 3. The base 40 of each cup 39 is securedby screws 42 to the chain links 30. Each chain link 30 is provided witha pair of side-by-side holes 43a and 43b, and one of the holes 43aregisters with a hole 44 in the base 40 of the vacuum cup 39.

Mounted on the upper surface of chain 20, as shown in FIG. 3, is aflexible plastic belt 45. A series of tubes 46 are formed integrallywith the belt and project through the aligned holes 43 and 44 in chainlinks 30 and vacuum cup 39. as shown in FIG. 3. One group of vacuum cups39 have holes 44 aligned with holes 43a, while a second group of vacuumcups have holes 44 aligned with holes 43b. Preferably the two groups ofvacuum cups are in alternating sequence. Accordingly, the tubes 46 arestaggered and are inserted within the aligned openings 43a and 44, or43b and 44.

The surface of each track 18 facing chain 20 is formed with four groovesor recesses 47, 48, 49 and 50. As seen in FIG. 5, grooves 47 and 48 arein side-by-side relation and grooves 49 and 50 are in side-by-siderelation and are spaced longitudinal from grooves 47 and 48.

A flexible trough or channel member 51 is mounted within grooves 47 and48, and similarly a flexible channel member or trough 52 is mounted ingrooves 49 and 50. Each channel member 51 and 52 includes a pair of sideby side channels 53 and the channels 53 of channel member 51 are locatedwithin grooves 47 and 48, while the

channels 53 of channel member 52 are located within grooves 49 and 50.Each channel member 51 and 52 is provided with a flexible peripheral lip54 which is engaged with and rides against of belt 45, as shown in FIG.3, thus providing a seal between the channels and the belt.

The channel members 51 and 52 are urged in a direction toward therespective chain 20 by a waffle spring 55 which is located between thecentral portion of each channel member and the lower surface of thetrack 18 as seen in FIG. 3.

As best illustrated in FIG. 4, a block 56 is formed integrally with theupper surface of each channel member 51 and 52, and a nipple 57 extendsoutwardly from each block. Each nipple is connected through an internalpassage in block 56 with the interior of the respective channel 53.Tubes 58 connect nipples 57 to manifold block 28 which is mounted on thetrack 18. A source of negative pressure or vacuum, such as a vacuumpump, is connected through conduit 59 to manifold 28 and throughsuitable valving in the manifold the negative pressure is appliedthrough tubes 58 to the four channels 53. The negative pressure is thenapplied from each channel 53 through tube 46 in belt 45 to thecorresponding vacuum cups 39. The use of the multiple channels 53, eachbeing individually connected to a source of vacuum, prevents the entireloss of vacuum to the robot if the robot should traverse an obstruction,crack or other surface deviation. For example, if the robot should movelongitudinally over an elongated crack with the crack being aligned withthe grooves 47 and 48, the vacuum in the channels 53 located in grooves47 and 48 may be lost, but the vacuum will be retained in the channels53 located in the grooves 49 and 50, thus preventing the robot fromfalling from a vertical or inclined surface. Similarly, if the robotshould move across a transverse crack the vacuum may be lost in a pairof side-by-side channels 53, but the other pair of side by side channelswill retain the vacuum to maintain the robot in contact with thesurface.

In addition, a flexible valve member 60 is connected by screw 60a to thebase 40 of each vacuum cup 39 and is in registry with hole 44. Valvemember 60 is contoured so that it is normally open, as shown in FIG. 3to permit vacuum to be drawn in cup 39. However, if cup 39 should travelover a crack or obstruction in surface 2 causing air to enter the cup,the pressure differential will move valve member 60 to a closed positionrelative to hole 44 to prevent the air entering cup 39 from flowing tothe manifold block 28.

The robotic device, as illustrated in FIGS. 1 and 2, can be used to movea working implement or attachment 61 across the surface 2 to be treated.The attachment 61 includes a frame 62, which is pivotally connected to apair of lugs 63 that extend rearwardly from generally L-shaped brackets64, that are connected to the rear frame member 12, as best in FIG. 2.Three yokes 66 are connected to frame 63 and a rotary buffer 67 ismounted for rotation in each yoke 66. The buffers 67 are designed to beindividually rotated by drive motors located internally of the buffers,not shown. Suitable shields 68 are connected to the yokes and extendpartially over the buffers 67 to confine spray from the buffers.

The buffers 67 are urged downwardly into contact with surface 2 by anair cylinder unit 69. Cylinder unit 69 includes a cylinder 70 and a rod72 is connected to one end of the cylinder and is pivotally connected toa pair of lugs 73 which project upwardly from housing 3. A piston isslidable within cylinder 70 and a piston rod 74, which is connected tothe piston, extends from the opposite end of the cylinder and ispivotally connected to lugs 75 that extend upwardly from frame 62. Byextending cylinder unit 69, down pressure can be applied through buffer67 to surface 2. By retracting the cylinder unit 69, the frame 62 andbuffers 67 can be pivoted upwardly out of contact with surface 2, asshown by the dashed lines in FIG. 1.

While the drawings illustrate the working implements to take the form ofrotary buffer 67, it is contemplated that various types of workingimplements can be substituted, such as scrubbers, waxers, paintapplicators and the like.

As a feature of the invention, a provision is incorporated to preventthe robot from falling from a vertical or inclined surface 2 in theevent there is a failure in the vacuum system. In this regard, a fan 76is mounted in the opening in flange 7 which extends upwardly fromhousing 3. Fan 76 includes a hollow vertical shaft 77 which is driven bya motor 78. Motor 78 is supported within the opening in flange 7 by aseries of diametrically extending braces 79.

A sensor, not shown, will sense the magnitude of the vacuum or negativepressure in the vacuum system. If the vacuum decreases to a pre-selectedvalue, the fan 76 will be operated to create a negative pressure withinthe housing 3 to prevent the robot from falling from surface 2. Thebrush seal 11 which is mounted on the peripheral edge of the housing 3and is engaged with the surface 2, cooperates with the fan to enable anegative pressure to be created within the housing.

FIG. 7 illustrates a preferred embodiment of the invention in which therobot 1 is utilized for nondestructive inspection of an aircraft. Inthis embodiment, the retro-reflector or cat's eye 9 is mounted on theupper end of a rod 80 that is slidable within the hollow fan shaft 77.The lower portion of rod 80 extends freely through motor 78 and thelower end of the rod 1 is provided with a sensor or shoe 82, which isadapted to ride on the surface 2 of aircraft 83. Sensor 82 is biaseddownwardly against the aircraft surface 2 by a coil spring 84, which isinterposed between the motor 78 and the upper surface of the sensor.

In the non-destructive inspection system, one or more robots 1 aremounted to travel across the surface of the aircraft 83, as illustratedin FIG. 8. In practice, three robots 1 can be utilized along with sixlaser tracking units 85 when inspecting a large commercial aircraft. Asshown in FIG. 7, a movable carriage 86 is associated with each robot andincludes a vacuum pump, that is connected by a suitable conduit 87 tothe manifolds 28 on the robot. In addition, electric feed lines notshown, are connected between the carriage 86 and the robot 1. Asillustrated in FIG. 7, one of the carriages 86 is mounted to travel onan overhead track 88 and is connected to a robot 1 which is adapted tomove across the upper surfaces of the aircraft 83, while a secondcarriage 85 travels on the ground and is operably connected to a secondrobot 1 that traverses the lower surface of the aircraft.

In carrying out the non-destructive inspection, the vacuum system isinitially started to create a vacuum in the vacuum cups and enable therobot to adhere to the surface of the aircraft 83. The aircraft hascertain tooling locations, or depressions, located at various positionson the buoyancy line, which are used as reference points to takedimensions during the manufacture and set-up of the aircraft. Thesedepressed reference points are generally referred to as fiducials.Through a radio controlled unit, the motors 24 on the robot 1 are thenactuated to move the robot over the aircraft surface until the sensor 82is engaged with a fiducial. Through the computer of the laser system,this is established as an origin point.

As a large aircraft generally has a number of fiducials, the robot ismoved and engaged with each fiducial to obtain a series of originpoints.

The desired operating program as selected in the computer, then actuatesthe program to operate the motors 24 to move the robot in the desiredpath of travel

on the aircraft surface. At this time, the interior of the aircraft isunder atmospheric pressure. As the robot moves across the aircraftsurface the sensor 82 will ride on the surface and will move relative tothe frame of the robot.

As described in the tracking system of U.S. Pat. No. 4,714,339, a laserbeam is directed from tracking unit 85 to the target, which is theretro-reflector 9 mounted on housing 3, and the retro-reflector reflectsa beam back to a tracking unit 85. Photosensors attached to the trackingunit provide error signals to a servo system, which controls optics atthe tracking unit to provide the direction necessary to accomplish thecoincidence of the beams. The separation of the incident or source beamand the reflected beam are measured and by measuring the direction ofthe beams relative to the tracking unit or tracking point, the targetcan be located in spatial coordinates and the orientation of theretro-reflector 9 can be continuously determined, thus providing asurface map of the aircraft.

After the surface mapping of the entire aircraft has been completed, theinterior of the aircraft is then pressurized at about 1 atmosphere ofpressure and the surface mapping operation is repeated. If any portionof the aircraft surface shows a deviation under pressurized conditionsbeyond a given tolerance it can indicate a potential defect in thesurface, such as a crack or faulty rivet. Any potential defective areacan then be manually inspected.

By using the robot 1 in conjunction with a laser tracking system,surface mapping of the aircraft can be accomplished to determinepotential areas of defect without the necessity of stripping paint fromthe aircraft surface and without the need of a manual inspection of theentire aircraft surface. As the paint stripping, manual inspection,repainting and waxing operations are eliminated, the overall time andcost for the inspection is greatly reduced.

As a further and important advantage, the invention eliminates the needof incorporating pollution control equipment, which is necessary fornormal paint stripping operations. Stripping of the paint from a largecommercial aircraft, such as a Boeing 747, normally requires more than1,000 gallons of solvent, such as methylene chloride. As the solvent istoxic, and creates a potential environmental hazard, pollution controlequipment is necessary to restrict the escape of solvent vapors.

It is preferred that tracks 18, as well as frame 4, be constructed offlexible plastic material so that the robot can conform to contouredsurfaces.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims, particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

I claim:
 1. A robotic apparatus for traversing a surface, comprising asupporting structure, a pair of parallel tracks, an endless membermounted for travel on each track, drive means for driving each endlessmember in a path of travel, each track including a first recess and asecond recess, said recesses disposed in side-by-side laterally spacedrelation, said recesses each having an open side facing the respectiveendless member, a plurality of vacuum cups mounted on each endlessmember, first port means providing communication between said firstrecess of each track and a first group of vacuum cups, second port meansproviding communication between the second recess of each track and asecond group of said vacuum cups, and vacuum means for creating anegative pressure in each recess.
 2. The apparatus of claim 1, whereinsaid drive means comprises a pair of separate drive members each beingoperably connected to an endless member.
 3. The apparatus of claim 1,wherein said endless member comprises a link chain.
 4. The apparatus ofclaim 1, and including a belt secured to a surface of each endlessmember and disposed to ride against the respective track.
 5. Theapparatus of claim 4, wherein each belt includes a plurality tubularmembers, each tubular member disposed in said first and second portmeans to provide communication between each recess and the respectivevacuum cup.
 6. The apparatus of claim 1, wherein said tracks areflexible and enable said robotic apparatus to conform to contouredsurfaces.
 7. The apparatus of claim 1, wherein said supporting structureincludes an outer open bottom hood, and a flexible brush seal mounted onthe peripheral edge of the hood bordering the open bottom and disposedto sealingly engage said surface.
 8. The apparatus of claim 7, whereinsaid hood is provided with an aperture spaced from said open bottom,said apparatus including blower means communicating with said aperturefor creating a negative pressure within the hood to prevent the roboticapparatus from falling from said surface in the event of a failure ofsaid vacuum means.
 9. The apparatus of claim 8, wherein said aperture isdisposed in the upper surface of said hood and said blower means ismounted in said aperture.
 10. The apparatus of claim 1, and including aworking attachment connected to said supporting surface and constructedto perform a working operation on the surface.
 11. The apparatus ofclaim 10, and including means for applying down pressure to saidattachment to urge said attachment against said surface.
 12. A roboticapparatus for traversing a surface, comprising a supporting frame, apair of parallel tracks, a pair of endless members each mounted fortravel in an upper run and a lower run, the lower run of each endlessmember being guided in travel on the respective track, a pair ofseparate drive members each operably connected to one of said endlessmembers to move the endless member in travel on said track, each trackincluding a first recess, a second recess, a third recess and a fourthrecess, said recesses each having an open side facing the respectiveendless member, said first and second recesses being spaced laterally ofeach other and said third and fourth recesses being spaced laterallyfrom each other and being longitudinally aligned with the first andsecond recesses respectfully, a plurality of vacuum cups mounted on eachendless member, a plurality of first ports in each endless memberproviding communication between the first and third recesses and a firstgroup of said vacuum cups, a plurality of second ports in each endlessmember providing communication between the second and fourth recessesand a second group of said vacuum cups, and vacuum means for creating anegative pressure in each recess.
 13. The apparatus of claim 12, andincluding an endless belt mounted on a surface of each endless memberand disposed to engage the respective track as the endless member movesin its path of travel, said belt having a plurality of holes eachaligned with the ports in the endless member.
 14. A robotic apparatusfor traversing a surface, comprising a supporting frame, a pair ofendless members mounted for movement on said frame, each endless memberhaving an upper run and a lower run disposed to engage the surface,drive means operably connected to said endless members for moving saidendless members in a path of travel to move said apparatus in adirection over the surface, a plurality of vacuum cups mounted on eachendless member, vacuum means for creating a negative pressure in thevacuum cups disposed in the lower run of each endless member, and alaser beam retro reflector mounted on the frame in position to receiveand reflect a laser beam from a laser tracking unit.
 15. The apparatusof claim 14, wherein said retro reflector is mounted generally centrallyof said frame and projects upwardly above said frame.
 16. A roboticapparatus for traversing a surface, comprising a supporting frame, apair of endless members mounted for movement on said frame, each endlessmember having an upper run and a lower run disposed to engage thesurface, drive means operably connected to said endless members formoving said endless members in a path of travel to move said apparatusin a direction over the surface, a plurality of vacuum cups mounted oneach endless member, vacuum means for creating a negative pressure inthe vacuum cups disposed in the lower run of each endless member,surface sensing means mounted on the frame and disposed to ride on thesurface as the apparatus traverses said surface, said surface sensingmeans being movable in accordance with deviations in said surface in asecond direction at an angle to the direction of movement of theapparatus, and means responsive to movement of said surface sensingmeans in said second direction to generate a surface map of saidsurface.
 17. The apparatus of claim 16, wherein said surface sensingmeans comprises a sensing member, and means for mounting said sensingmember for movement in said second direction, said second directionbeing generally normal to a plane extending through the lower runs ofsaid endless members.
 18. The apparatus of claim 17, and includingbiasing means for biasing the sensing member toward said surface. 19.The apparatus of claim 16, wherein said sensing means comprises asensing member disposed to ride on said surface, a support to carry saidsensing member, means for mounting the support for sliding movementrelative to said frame in said direction, and biasing means for biasingthe sensing member toward said surface.
 20. A combination, comprising arobotic apparatus for traversing a surface and having a supportingframe, a pair of endless members mounted for movement on said frame,each endless member having an upper run and a lower run disposed toengage the surface, drive means operably connected to said endlessmembers for moving said endless members in a path of travel to move saidapparatus in a direction over the surface, a plurality of vacuum cupsmounted on each endless member, vacuum means for creating a negativepressure in the vacuum cups disposed in the lower run of each endlessmember, and a laser tracking unit including laser beam generating meanslocated at a remote location relative to said robotic apparatus forgenerating an incident laser beam, a laser beam retro reflector mountedon the frame in position to receive and reflect said incident laserbeam, said laser tracking unit also including means for comparing theincident beam and the reflected beam to provide a measurement of thespatial coordinates of the retro reflector.
 21. A robotic apparatus fortraversing a surface, comprising a supporting structure, a pair ofparallel tracks, an endless member mounted for travel on each track,drive means for driving each endless member in a path of travel, eachtrack including a first recess and a second recess, said recesses eachhaving an open side facing the respective endless member, a plurality ofvacuum cups mounted on each endless member, first port means providingcommunication between said first recess of each track and a first groupof vacuum cups, second port means providing communication between thesecond recess of each track and a second group of said vacuum cups, aflexible channel member disposed in each recess, each channel memberhaving an open side facing the respective endless member and having aflexible peripheral lip disposed in bearing engagement with the endlessmember, biasing means for biasing each channel member toward the endlessmember, and vacuum means for creating a negative pressure in eachrecess.
 22. A robotic apparatus for traversing a surface, comprising asupporting structure, a pair of parallel tracks, an endless membermounted for travel on each track, drive means for driving each endlessmember in a path of travel, each track including a first recess and asecond recess, said recesses each having an open side facing therespective endless member, a plurality of vacuum cups mounted on eachendless member, first port means providing communication between saidfirst recess of each track and a first group of vacuum cups, second portmeans providing communication between the second recess of each trackand a second group of said vacuum cups, vacuum means for creating anegative pressure in each recess, said vacuum means including a manifoldmounted on each track and connected with a source of vacuum, and conduitmeans independently connecting said manifold with each of said recesses.23. A robotic apparatus for traversing a surface, comprising asupporting structure, a pair of parallel tracks, an endless membermounted for travel on each track, drive means for driving each endlessmember in a path of travel, each track including a first recess and ascold recess, said recesses each having an open side facing therespective endless member, a plurality of vacuum cups mounted on eachendless member, first port means providing communication between saidfirst recess of each track and a first group of vacuum cups, second portmeans providing communication between the second recess of each trackand a second group of said vacuum cups, vacuum means for creating anegative pressure in each recess, and valve means associated with eachport means for closing said port means in the event ambient air leaksinto said vacuum cup.
 24. The apparatus of claim 23, wherein said valvemeans comprises a valve member disposed within said vacuum cup andmovable between a closed position wherein the valve member encloses saidport means and an open position.
 25. The apparatus of claim 24, whereinsaid valve member is a flexible strip.
 26. A robotic apparatus fortraversing a surface, comprising a supporting frame, a pair of endlessmembers mounted for movement on said frame, each endless member havingan upper run and a lower run disposed to engage the surface, drive meansoperably connected to said endless members for moving said endlessmembers in a path of travel to move said apparatus in a direction overthe surface, a plurality of vacuum cups mounted on each endless member,vacuum means for creating a negative pressure in the vacuum cupsdisposed in the lower run of each endless member, an open bottom hoodmounted on the frame and enclosing said endless members, a flexible sealmounted on the peripheral edge of the hood bordering the open bottom anddisposed to sealingly engage said surface, negative pressure meansseparate from the vacuum means for creating a negative pressure withinthe hood in the event of failure of said vacuum means to prevent saidapparatus from falling from said surface and means responsive to adecrease in vacuum generated by said vacuum means below a preselectedvalue for operating said negative pressure means.
 27. A roboticapparatus for traversing a surface, comprising a supporting frame, apair of endless members mounted for movement on said frame, each endlessmember having an upper run and a lower run disposed to engage thesurface, drive means operably connected to said endless members formoving said endless members in a path of travel to move said apparatusin a direction over the surface, a plurality of vacuum cups mounted oneach endless member, each vacuum cup having an open side to be disposedin contact with said surface and having a passage communicating withsaid open side, vacuum means communicating with the passage of eachvacuum cup for creating a negative pressure in the vacuum cups disposedin the lower run of each endless member, and valve means associated witheach passage for closing said passage in the event ambient air leaksinto said vacuum cup.
 28. The apparatus of claim 27, wherein said valvemeans comprises a flexible valve member disposed within said vacuum cupand movable between a closed position wherein the valve member enclosessaid passage and an open position.